Radio transmitting system



Oct. 9, 1928.

L. DE FOREST RADIO TRANSMITTING SYSTEM Filed Feb. 18, 1918 20 a J I j m 2/ m1 w Z2 r 4' n I IF Patented Oct. 9, 1928.

UNITED STATES PATENT OFFICE.

LEE DE FOREST, OP' NEW YORK, N. Y., ASSIGNOR TO DE FOREST RADIO TELEPHONE &;

TELEGRAPH COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELA- WARE.

RADIO TRANSMITTING SYSTEM.

Application filed February 18, 1919. Serial No. 277,826.

This invention relates to radiotransmit ting systems.

The object of the invention is to provide a radio transmitting system which is simple 5 and effective in circuit arrangement, andwhich is particularly adapted for use at high power transmission stations.

A further object of the invention is to provide a transmitting 'system of the character I described which permits the use of a source of alternating current.

A further object of the invention is to provide a system in which a combination of re tifying and oscillating qualities of a three electrode oscillator, or oscillion is utilized.

Further objects of the invention will appear more fully hereinafter. 4

The invention consistdsubstantially of the combination location, relative arrangement 0 of parts, and the circuits employed in connection therewith, all as will be more fully hereinafter set forth, as set forth in the accompanying drawing, and finallypointed out in the appended claims.

Referring to the drawing Fig. 1 is a diagrammatic view of a transmitting system embodying my invention.

Fig. 2 is a similar view of a modified form of transmitting system.

9 Figs. 3 and 4 are diagrammatic views of the current waves and their form inserted for the purpose of more clearly describing my invention.

The same part is designated by the same reference character wherever it occurs throughout the several views. I

- In transmitting stations, and particularly in stations for high power work, and where an oscillation generator of the three electrode or oscillion type is employed, it is obviously of advantage to employ an alternating current source which is high in voltage rather than high in current.- Where a high current is employed it is necessary to have a comparatively large bulb or oscillion due to the fact that the electrodestherein are necessarily of large size. It is therefore desirable in order to keep the size of the three electrode oscillator, and consequently the expense thereof at a minimum, to use a rectifier for rectifying the alternating current before supplying it to the transmitting system. It is well understood in the art that where the alternating current supplied is in the form of the wave shown in 3, where rectificatems have been devised and employed wherein the portion of the current indicated by dotted lines in Fig. 3 is likewise utilized and supplied to the oscillating system so that a pulsating direct current similar in character to that indicated in Fig. 4 is secured, thereby utilizing both the positive and negative portions of the alternating current employed in connection with the transmitting system. Such a system I show and describe in my Patent No. 979,276, issued December 20, 1910, and the principle of my present invention is closely related to the invention shown, described and claimed in my above named patent; In my present invention, however, I so arrange my circuits in connection with the three electrode oscillator that the alternating current is supplied to the oscillating system directly without the use of independent rectifiers and thus secure a functioning of the three electrode device as a combined rectifier and oscillator, thereby providing a system which is self-contained, extremely efficient, and being of fewer parts and pieces of apparatus, much simpler in construction and easier to install, maintain and operate.

Referring to Fig. 1, as one embodiment of my invention, I show the usual antenna earth system, comprising the antenna 1, inductance 2, variable capacity 3 in series therewith, which antenna system is grounded, for example, to earth at 4. The three electrode oscillator or oscillion is'indicated at 5, and in the form shown consists of the evacuated vessel containing the plate electrodes 6 and 7 filament electrode 8, and the grid electrodes 9, which are joined together, preferably within the vessel. and are interposed between the plates 6 and 7 and the filament. The filament is heated by the usual current source, for example, battery 10, and is controlled by the variable resistance 11 in the usual well known maner. The plate electrode 6 is connected to one terminal of the secondary 12 of the transformer, the other terminal of which is connected to the plate electrode 7 The middle of the secondary coil of the transformer 12 is connected to the filament electrode as shown. The plate electrodes 6 and 7 are connected to'one terminal of the second ary coil 13 which is inductively related to the inductance 2 of the antenna earth system. The other terminal of the secondary coil 13 is connected to the grid electrodes 9 and included in said circuit is the usual signalling device, which for the purpose of illustration,

is indicated as a signalling key at 14 connected in series with a high resistance 15, which key and resistance is shunted around the condenser 16. The midpoint of the coil 13 is connected to the filament 8. Primary coil 17 of the transformer leading to the oscillating system is connected to a suitable source of alternating current. In the foregoing system it will be seen that alternating current is supplied through the transformer coils 17 and 12 to the oscillating system and the combined rectifier and oscillator 5. The current of one potential, say for example, negative currentof the alternating current supplied through the. transformer 17, 12 is supplied to the plate electrode 6, and the current of the other potential, for example, positive current from said alternating current source is supplied to the plate electrode 7. Condensers 19 and 20 are included in the leads connecting the respective plate electrodes 6 and 7 to each other and to the inductance or transformer coil 13 to prevent interference between the two plate electrodes in their respective functioning. Thus it will be seen that current of one potential will be passing between the plate 6 and filament 8, and current of a different potential will be passing between plate 7 and filament 8. It will be apparent therefore that if the electrodes are connected as above outlined to the usual oscillating circuit, for example, the regenerative circuit above described, that both the positive and negative potentials of the alternating current supplied to the oscillating system is utilized, and that a highly efficient transmitting station suitable for high power purposes is secured. To-prevent the high frequency oscillations set up in the system from reaching the transformer coil 12 it is desirable to insert in the leads therefrom to the respective electrodes 6 and 7choke coils indicated at 21 and to insert reservoir condensers indicated at 22 in the leads connecting the opposite terminals of the coil 12 with the filament lead connected to the mid point of the coil 12. In this manner, in a single self-contained system, it will be apparent that practically a continuous E. M. F. is supplied to .the oscillating system.

In Fig. 2 I show the same idea applied to the tickler transmitter system which-has been adopted and used to great: extent commercially, the particular subject matter of which is shown and described in my Patent 1,417,662, issued May 30, 1922, wherein the plate electrode 6 is connected through a conelectrodes.

denser 25. to the antenna earth system at a point intermediate the inductance 2 and the variablecapacity 3, and the plat-e electrode 7 is similarly connected through the condenser 26 to the antenna earth systenm The filament electrode 8 is similarly directly connected to the antenna earth system at a point preferably between the variable capacity 3 and the ground 4 through condenser 27, and v the grid filament circuit, including therein 15 the signaling device, is inductively associated through coil 28 with the inductance 2 of the antenna earth system. The operation of the system thus described, it will be apparent, in so far as the combined oscillating and rectifying action is concerned is identical gith 1that above described with reference to lg. Many other modifications and t ariations of my invention will readily occur to those skilled in the art, and various other transmitting circuits employing the three electrode oscillator can readily beused with my present invention, and therefore I desire to have the foregoing specific elements regarded in the illustrative sense rather than in a limiting sense. r J

Having now set forth the objects and nature of my invention, and having shown and described several systems embodying the principles thereof, what I claim as new and useful and of my own invention and desire to secure by Letters Patent is 1. In a transmitting system, the combination with a vessel having a hot electrode, a 1

Vice included in said oscillating circuit.

2. In a transmitting system, the combination with a vessel having a hot electrode, a pair of separated plate electrodes and a grid electrode interposed between each of said plate electrodes and said hot electrode, an oscillating circuit connecting two of said electrodes, a source of alternating currents, and a transformer coil connected at its respective terminals with said plate electrodes and associated with said source, and choke coils interposed between the ends of said coiland said plate electrodes.

3. In a transmitting system, the combination with a vessel having a hot and a plurality" of cold electrodes, an oscillating circuit connecting two of said'cold electrodes, asource of alternating currents, a transformer coil connected at its respective terminals with two of said cold electrodes and associated with said source, and choke coils interposed between the ends of said coil and said cold 4. In a transmitting system, the combinaterminals with two of said electrodes and astion with a vessel having a hot cathode, two sociated with said source and impedance de- 10 anodes and a control electrode for each anode, vices in the connection to each terminal. said anodes being at a difierent distance from In testimony whereof I have hereunto set 5 said hot cathode than said control electrodes, my hand on this 10th dayof February A. D.,

an oscillating circuit connecting two of Said 1919. v electrodes, 'a source of alternatlng currents, a transformer coil connected at its respective i LEE nn FOREST. 

